Beam-forming network

Abstract

A satellite communications system employs separate subsystems for providing broadcast and point-to-point two-way communications using the same assigned frequency band. The broadcast and point-to-point subsystems employ an integrated satellite antenna system which uses a common reflector (12). The point-to-point subsystem achieves increased communication capacity through the reuse of the assigned frequency band over multiple, contiguous zones (32, 34, 36, 38) covering the area of the earth to be serviced. Small aperture terminals in the zones are serviced by a plurality of high gain downlink fan beams (29) steered in the east-west direction by frequency address. A special beam-forming network (98) provides in conjunction with an array antenna (20) the multiple zone frequency address function. The satellite (10) employs a filter interconnection matrix (90) for connecting earth terminals in different zones in a manner which permits multiple reuse of the entire band of assigned frequencies. A single pool of solid state transmitters allows rain disadvantaged users to be assigned higher than normal power at minimum cost. The intermodulation products of the transmitters are geographically dispersed.

What is claimed is: 
     
       1. Apparatus for simultaneously forming a plurality of antenna beam signals for transmission by an antenna to a plurality of different zones using a plurality of transmit signals respectively corresponding to said zones, wherein each of the transmit signals includes a plurality of subsignals having respective preselected frequencies and each destined to be received at an associated location in the corresponding zone, comprising: a first plurality of lines for respectively carrying said plurality of transmit signals and each including an input for receiving a corresponding one of said transmit signals; and   a second plurality of spaced apart lines intersecting said first plurality of lines at crossover points of said first and second plurality of lines, each of said second plurality of lines being coupled with each of said first plurality of lines at said crossover points such that a portion of the energy of each of the transmit signals carried by each of said first plurality of lines is transferred to each of said second plurality of lines, each of said second plurality of lines having an output for continuously outputting said antenna beam signals,   the distance between adjacent crossover points and the width of each of said first plurality of lines being preselected to produce a desired shift in phase of each of said subsignals whereby said subsignals are continuously steered to respectively associated locations in corresponding zones as a function of the frequencies of said subsignals,   said second plurality of lines extending essentially radially away from a reference point such that said second plurality of lines diverge from each other,   said first plurality of lines extending circumferentially about said reference point and being radially spaced relative to said reference point such that the distance between adjacent crossover points increase with increasing radial distance of the crossover points from said reference point.   
     
     
       2. The apparatus of claim 1, wherein said first plurality of lines includes a plurality of transmission lines for conveying electromagnetic energy and said second plurality of lines includes a plurality of electromanetic energy waveguides. 
     
     
       3. The apparatus of claim 2, wherein each of said transmission lines is coupled with each of said waveguides by an electromagnetic wave crossguide coupler. 
     
     
       4. The apparatus of claim 1, wherein at least two of said first plurality of lines are substantially contiguous to each other. 
     
     
       5. The apparatus of claim 1, wherein at least two of said first plurality of lines are spaced from each other. 
     
     
       6. Apparatus for forming substantially simultaneously a plurality of antenna beam signals for transmission by an antenna to a plurality of different locations and using a plurality of transmit signals each including a plurality of subsignals having respective preselected frequencies and respectively destined to be received at said different locations, comprising: a first set of lines for respectively carrying said plurality of transmit signals and arranged in a generally arcuate pattern, said first set of lines including a plurality of inputs for respectively receiving said transmit signals;   a second set of lines extending radially outward from a reference point and being circumferentially spaced apart from each other, said second set of lines interacting said first set of lines at crossover points and having a plurality of respectively associated outputs each operative for continuously outputting said antenna beam signals, said first set of lines being radially spaced from each other relative to said reference point; and   means for coupling said first and second sets of lines with each other at each of said crossover points and allowing a portion of the energy of each of the transmit signals carried by said first set of lines to be transferred to each of said second set of lines at said crossover points, the antenna beam signals output by each of said second set of lines being shifted in phase in accordance with the distance traveled by said transmit signals along said first set of lines between said crossover points and in accordance with the width of said first set of lines, the phase of each transmit signal determining the location of the transmit signal to be transmitted by said antenna, and the direction of the antenna beam signals transmitted by said antenna to said different locations being continuously steered as a function of the frequencies of the subsignals.   
     
     
       7. The apparatus of claim 6, wherein the distance between adjacent ones of said crossover point increases with increasing radial distance away from said reference point. 
     
     
       8. The apparatus of claim 6, wherein said coupling means includes a plurality of crossguide couplers. 
     
     
       9. The apparatus of claim 6, wherein each of said first set of lines possesses a constant radius measured from said reference point. 
     
     
       10. The apparatus of claim 6, wherein each of said first set of lines includes a transmission line and each of said second set of lines includes an electromagnetic waveguide. 
     
     
       11. The apparatus of claim 6, wherein the distance between each adjacent pair of crossover points along each of said first set of lines is substantially constant. 
     
     
       12. Apparatus for simultaneously forming a plurality of satellite downlink antenna beams for transmission to corresponding downlink locations in a plurality of different zones covering an area of the earth, said beams being formed using a plurality of transmit signals each carrying a plurality of subsignals having respective preselected frequencies and destined to be received at a downlink location in a corresponding one of said zones and originating from an uplink location in another of said zones, comprising: a first plurality of lines for respectively carrying said plurality of transmit signals and each including an input for receiving a corresponding one of said transmit signals;   a second set of spaced apart lines crossing said first set of lines at crossover points and each including an output for continuously outputting all of said antenna beam signals, said first set of lines being arranged in an arc having a constant radius relative to a reference point and said second set of lines extending radially outward from said reference point; and   means for coupling each of said first set of lines with each of said second set of lines at said crossover points to allow a portion of the energy of each of said transmit signals carried by each of said first set of lines to pass to each of said second set of lines,   said first and second sets of lines being arranged to produce a desired shift in the phase of said subsignals such that said phase shift determines the zone in which said subsignals are received and the antenna beam signals are continuously steered to the locations within the zones as a function of the frequencies of said subsignals.   
     
     
       13. The apparatus of claim 12, including converting means for receiving a plurality of receive signals respectively associated with said zones and each including a plurality of channels carrying subsignals originating from uplink locations in the corresponding zone and destined to be received at a location in a different zone, and for converting said receive signals into said transmit signals. 
     
     
       14. The apparatus of claim 13, wherein said converting means includes: a plurality of input terminals for respectively receiving said receive signals,   a plurality of output terminals respectively coupled with the inputs of said first plurality of lies for respectively outputting said transmit signals to said first plurality of lines, and   interconnection means for interconnecting each of said input terminals with each of said output terminals and for filtering each of said receive signals such that the subsignals of each of said receive signals are delivered to the output terminals only on certain of said channels.   
     
     
       15. The apparatus of claim 14, wherein said interconnection means includes a plurality of sets of filters each being associated with one of said receive signals, each of said sets of filters, including a plurality of groups of said filters, each group being associated with a corresponding transmit signal wherein each filter in each set thereof is operative to filter through a corresponding one of said channels from one of said input terminals to one of said output terminals. 
     
     
       16. The apparatus of claim 14, wherein said interconnection means includes a plurality of sets of filters each of said sets being connected to a corresponding one of said input terminals to receive an associated receive signal, each of sets including a plurality of groups of filters for routing the subsignals on corresponding preselected channels from a corresponding input terminal to a corresponding one of said output terminals. 
     
     
       17. The apparatus of claim 16, wherein each of said output terminals is connected with only certain of the filters in each set thereof such that the subsignals are interconnected between an uplink location and downlink location in different zones through said certain channels. 
     
     
       18. Apparatus for forming substantially simultaneously a plurality of antenna beam signals for transmission by an antenna to a plurality of different locations and using a plurality of transmit signals each including a plurality of subsignals having respective preselected frequencies and respectively destined to be received at said different locations, comprising: a first set of lines for respectively carrying said plurality of transmit signals and arranged in a generally arcuate pattern, said first set of lines including a plurality of inputs for respectively receiving said transmit signals;   a second set of lines extending radially outward from a reference point and being circumferentially spaced apart from each other, said second set of lines intersecting said first set of lines at crossover points and having a plurality of respectively associated outputs each operative for continuously outputting said antenna beam signals, the distance between adjacent ones of said crossover points increasing with increasing radial distance away from said reference point; and   means for coupling said first and second set of lines with each of said crossover points and allowing a portion of the energy of each of the transmit signals carried by said first set of lines to be transferred to each of said second set of lines at said crossover points, the antenna beam signals output by each of said second set of lines being shifted in phase in accordance with the distance traveled by said transmit signals along said first set of lines between said crossover points and in accordance with the width of said first set of lines, the phase of each transmit signal determining the location of the transmit signal to be transmitted by said antenna and the direction of the antenna beam signals transmitted to said different locations being continuously steered as a function of the frequencies of said subsignals.   
     
     
       19. Apparatus for forming substantially simultaneously a plurality of antenna beam signals for transmission by an antenna to a plurality of different locations and using a plurality of transmit signals each including a plurality of subsignals having respective preselected frequencies and respectively destined to be received at said different locations, comprising: a first set of lines for respectively carrying said plurality of transmit signals and arranged in a generally arcuate pattern, said first set of lines including a plurality of inputs for respectively receiving said transmit signals, said first of lines possessing a constant radius measured from a reference point;   a second set of lines extending radially outward from said reference point and being circumferentially spaced apart from each other, said second set of lines intersecting said first set of lines at crossover points and having a plurality of respectively associated outputs each operative for continuously outputting said antenna beam signals; and   means for coupling said first and second sets of lines with each other at each of said crossover points and allowing a portion of the energy of each of the transmit signals carried by said first set of lines to be transferred to each of said second set of lines at said crossover points, the antenna beam signals output by each of said second set of lines being shifted in phase in accordance with the distance traveled by said transmit signals along said first lines between said crossover points and in accordance with the width of said first set of lines, the phase of each transmit signal determining the location of the transmit signal to be transmitted by said antenna and the direction of the antenna beam signals transmitted to said different locations being continuously steered as a function of the frequencies of said subsignals.